1. Field of the Invention
This disclosure relates to fuel vapor treating apparatuses for treating fuel vapor vaporized in a fuel tank of a vehicle, in particular, relates to the fuel vapor treating apparatuses each having a high thermal conductive honeycomb core for improving heat-transfer efficiency in the fuel vapor treating apparatus.
2. Description of the Related Art
Japanese Laid-Open Patent Publication No. 2009-191688 discloses an adsorbent canister (fuel vapor treating apparatus) having a housing that defines an adsorption chamber therein. The adsorption chamber is filled with an adsorbent capable of temporarily trapping fuel vapor and then desorbing the fuel vapor due to airflow in the adsorption chamber.
The housing of the adsorbent canister has a grid-like partition dividing the adsorption chamber into a number of elongated spaces, which are filled with the adsorbent. The adsorbent is formed in an elongated pellet shape from powder of activated carbon. In usual, the adsorbent canister is filled with granule-shaped activated carbon.
The adsorbent such as activated carbon generally has low thermal conductivity and has a temperature-dependent adsorption capacity. That is, the adsorption capacity of the adsorbent for the fuel vapor is larger at higher temperature but is smaller at lower temperature. In addition, because adsorption of the fuel vapor onto the adsorbent is exothermic reaction, when the adsorbent adsorbs the fuel vapor, temperature of the adsorbent increases and thus adsorption ability of the adsorbent for the fuel vapor decreases with increase of temperature. On the other hand, because desorption of the fuel vapor from the adsorbent is endothermic reaction, when the adsorbent desorbs the fuel vapor, temperature of the adsorbent decreases and thus desorption ability of the adsorbent decreases with decrease of temperature. In this disclosure, adsorption ability and desorption ability of the adsorbent are referred to collectively as “adsorption and desorption ability”. And, adsorption and desorption of the adsorbent are referred to collectively as “adsorption and desorption”.
In the adsorbent canister having the adsorption chamber filled with the adsorbent, when the adsorbent adsorbs the fuel vapor, temperature increase in a center region of the adsorption chamber is larger than that in an outer region of the adsorption chamber. Thus, adsorption ability of the adsorbent in the center region becomes lower than that in the outer region. Whereas, when the adsorbent desorbs the fuel vapor, temperature decrease in the center region is larger than that in the outer region. Thus, desorption ability of the adsorbent in the center region becomes lower than that in the outer region. Accordingly, when adsorbing and desorbing the fuel vapor, adsorption and desorption ability of the adsorbent in the center region significantly decreases compared with that in the outer region. Therefore, there has been a need for improved adsorbent canisters.